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Alabama Combination Vehicles Test – 20 Questions with Answers

Test your knowledge of combination vehicles with 20 Alabama CDL practice questions covering coupling and uncoupling, fifth wheels, trailer off-tracking, rollover risks, air lines, trailer brakes, inspections, and safe operation of tractor-trailer combinations.

20
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15 min
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Medium
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  1. 1. What is the main purpose of the fifth wheel on a tractor?

    • A. To connect the tractor to the trailer
    • B. To store compressed air
    • C. To control the trailer lights
    • D. To support the engine
    Show answer

    A. To connect the tractor to the trailer

    The fifth wheel provides the coupling connection between the tractor and the semi-trailer.

  2. 2. What part of the trailer connects with the fifth wheel?

    • A. Kingpin
    • B. Landing gear
    • C. Mud flap
    • D. Axle shaft
    Show answer

    A. Kingpin

    The trailer's kingpin locks into the fifth wheel to create the tractor-trailer connection.

  3. 3. What should you check to make sure a trailer is properly coupled to the tractor?

    • A. The fifth-wheel locking mechanism
    • B. Only the trailer paint
    • C. Only the mud flaps
    • D. The driver's seat
    Show answer

    A. The fifth-wheel locking mechanism

    The fifth-wheel jaws or locking mechanism must properly secure the kingpin to prevent the trailer from separating.

  4. 4. What is trailer off-tracking?

    • A. When the trailer wheels follow a shorter path than the tractor during a turn
    • B. When the trailer loses electrical power
    • C. When the trailer brakes fail
    • D. When the trailer becomes disconnected
    Show answer

    A. When the trailer wheels follow a shorter path than the tractor during a turn

    During a turn, the trailer wheels generally track inside the path of the tractor. This is known as off-tracking.

  5. 5. Why should a combination vehicle driver be especially careful when making a sharp turn?

    • A. The trailer may off-track toward the inside of the turn
    • B. The trailer always moves faster than the tractor
    • C. The steering wheel becomes locked
    • D. The engine automatically loses power
    Show answer

    A. The trailer may off-track toward the inside of the turn

    Trailer wheels generally follow a shorter path than the tractor during turns, so drivers must account for off-tracking.

  6. 6. What is one major danger of taking a curve too fast in a combination vehicle?

    • A. Rollover
    • B. Improved traction
    • C. Shorter stopping distance
    • D. Reduced trailer movement
    Show answer

    A. Rollover

    Combination vehicles have a greater rollover risk when curves are taken at excessive speeds, especially when heavily loaded.

  7. 7. What should you do before entering a sharp curve with a tractor-trailer?

    • A. Reduce speed before entering the curve
    • B. Accelerate through the curve
    • C. Brake hard halfway through the curve
    • D. Drive onto the shoulder
    Show answer

    A. Reduce speed before entering the curve

    Reducing speed before the curve helps maintain control and reduces the risk of rollover or loss of traction.

  8. 8. What is the purpose of the tractor protection system?

    • A. To protect the tractor's air supply if the trailer separates
    • B. To increase the tractor's engine power
    • C. To control the trailer's cargo
    • D. To increase tire pressure
    Show answer

    A. To protect the tractor's air supply if the trailer separates

    The tractor protection system helps prevent loss of air from the tractor if the trailer becomes separated or develops a serious air-line problem.

  9. 9. What is the purpose of the trailer air supply control?

    • A. To control the supply of air to the trailer's air brake system
    • B. To control engine fuel
    • C. To adjust tire pressure
    • D. To control the tractor's headlights
    Show answer

    A. To control the supply of air to the trailer's air brake system

    The trailer air supply control allows compressed air to be supplied to the trailer's air brake system.

  10. 10. What should you check when connecting the air lines between a tractor and trailer?

    • A. That the lines are properly connected and free from damage or leaks
    • B. Only the color of the lines
    • C. Only the length of the lines
    • D. That the lines are disconnected
    Show answer

    A. That the lines are properly connected and free from damage or leaks

    Air lines must be properly connected and inspected for damage, leaks, and secure fittings.

  11. 11. What should you inspect on the electrical cord connecting the tractor and trailer?

    • A. It should be properly connected and free from damage
    • B. It should be disconnected during driving
    • C. It should touch the road
    • D. It should be wrapped around the kingpin
    Show answer

    A. It should be properly connected and free from damage

    The electrical connection supplies power to the trailer's lights and other electrical systems, so it should be secure and undamaged.

  12. 12. What is the purpose of landing gear on a semi-trailer?

    • A. To support the front of the trailer when it is uncoupled
    • B. To control the trailer brakes
    • C. To steer the tractor
    • D. To increase engine power
    Show answer

    A. To support the front of the trailer when it is uncoupled

    Landing gear supports the front of a semi-trailer when it is disconnected from the tractor.

  13. 13. What should you do before uncoupling a trailer?

    • A. Secure the vehicle and trailer and follow the proper uncoupling procedure
    • B. Release all connections while moving
    • C. Remove the kingpin first by hand
    • D. Leave the landing gear completely retracted
    Show answer

    A. Secure the vehicle and trailer and follow the proper uncoupling procedure

    The tractor and trailer must be secured and the proper sequence followed to prevent unexpected movement or damage.

  14. 14. What is a potential problem if a trailer's landing gear is not fully raised after coupling?

    • A. It could strike the roadway or other objects
    • B. It increases engine power
    • C. It improves fuel economy
    • D. It makes the trailer easier to steer
    Show answer

    A. It could strike the roadway or other objects

    Landing gear that is not fully raised can contact the roadway or obstacles and create a serious hazard.

  15. 15. Why is it important to maintain adequate following distance with a combination vehicle?

    • A. Combination vehicles may require considerable stopping distance
    • B. It prevents other vehicles from passing
    • C. It eliminates brake lag
    • D. It increases the vehicle's maximum speed
    Show answer

    A. Combination vehicles may require considerable stopping distance

    The size and weight of combination vehicles can increase stopping distance, so drivers need sufficient space to react and stop safely.

  16. 16. What is one danger of driving too fast on a wet road with a combination vehicle?

    • A. Loss of traction and increased risk of a skid or jackknife
    • B. Improved braking
    • C. Reduced stopping distance
    • D. Improved trailer tracking
    Show answer

    A. Loss of traction and increased risk of a skid or jackknife

    Wet roads reduce traction. Excessive speed can make it harder to maintain control and can contribute to skidding or jackknifing.

  17. 17. What is a jackknife?

    • A. When the tractor and trailer fold toward each other at the coupling
    • B. When the trailer tires become flat
    • C. When the fifth wheel disconnects normally
    • D. When the trailer lights stop working
    Show answer

    A. When the tractor and trailer fold toward each other at the coupling

    A jackknife occurs when the tractor and trailer move toward an excessive angle, often during a loss of traction or improper braking.

  18. 18. What should you do if the drive wheels begin to lose traction while operating a combination vehicle?

    • A. Ease off the accelerator and avoid sudden braking or steering
    • B. Accelerate hard
    • C. Apply maximum braking immediately
    • D. Turn sharply in the opposite direction
    Show answer

    A. Ease off the accelerator and avoid sudden braking or steering

    Sudden acceleration, braking, or steering can worsen a traction problem. Smooth control helps the tires regain traction.

  19. 19. Why should cargo weight be distributed properly in a combination vehicle?

    • A. To maintain vehicle stability and proper axle loading
    • B. To increase the vehicle's top speed
    • C. To eliminate the need for cargo securement
    • D. To make the trailer shorter
    Show answer

    A. To maintain vehicle stability and proper axle loading

    Proper weight distribution helps maintain stability, steering control, braking performance, and compliance with applicable weight limits.

  20. 20. After coupling a tractor to a trailer, what should you do before driving away?

    • A. Complete a thorough inspection of the coupling, connections, brakes, lights, and other equipment
    • B. Immediately accelerate onto the highway
    • C. Check only the fuel gauge
    • D. Leave the landing gear down
    Show answer

    A. Complete a thorough inspection of the coupling, connections, brakes, lights, and other equipment

    A complete post-coupling check helps verify that the tractor and trailer are securely connected and all required equipment is functioning properly.